1. Field of the Invention
The present invention relates to a boring device inserted into a lateral pipe to bore a pipe lining material that is inserted into a main pipe across the lateral pipe intersecting therewith.
2. Description of the Prior Art
A lining construction method has been proposed in the past for lining an existing pipe using a pipe lining material in order to rehabilitate an existing pipe without unearthing the pipe when a buried sewer line or other existing pipe has deteriorated with age (see JP-A 6-114939). The pipe lining material is a resin absorbent material composed of a tubular flexible nonwoven cloth impregnated with an uncured liquid curable resin (generally a thermosetting resin), formed so as to conform to the shape of the existing pipe. A highly airtight plastic film is attached to the outer circumferential surface of the resin absorbent material. In this construction method, fluid pressure is used to invert and insert the pipe lining material into the existing pipe, and, with the pipe lining material pressed against the internal circumferential surface of the existing pipe, heat is applied to the pipe lining material to cure the liquid thermosetting resin impregnated therein to provide a lined existing pipe.
Lateral pipes also join the main pipe of a sewer or the like. Therefore, when the pipe lining material is used to line the main pipe, it blocks the openings at which the lateral pipes join with the main pipe. A robot equipped with a boring device and a TV camera for operating inside a pipe is therefore placed in the main pipe and remote-controlled from above ground. The cutter (rotary blade) of the boring device is then rotated, and the portion of the pipe lining material that is blocking the end of the lateral pipe is bored through and removed (see FIGS. 5 through 8 of JP-A 2000-15509).
However, in this operation, the cutter of the boring device must be positioned in the longitudinal and vertical directions of the main pipe prior to boring. This positioning is performed while monitoring the inside of the main pipe using the TV camera, but since the inside of the main pipe is dark and yields poor visibility, errors sometimes occur in positioning, specifically, in the boring position.
In order to overcome this drawback, a method is employed whereby a hole saw connected to a flexible shaft for transmitting the rotational energy of a motor is inserted into the lateral pipe prior to the boring, and a pilot hole having a small diameter is formed from the side of the lateral pipe in the portion of the pipe lining material that blocks the opening at the end of the lateral pipe. After the pilot hole is formed, the TV camera is inserted into the lateral pipe, and boring is performed from the side of the abovementioned main pipe while monitoring the inside of the lateral pipe (see FIGS. 10 and 11 of JP-A 2000-15509).
However, in the method for forming a pilot hole from the side of the lateral pipe, the hole saw is supported by the flexible shaft so as to be able to move in the direction orthogonal to the longitudinal direction of the lateral pipe. Therefore, it is difficult to position the hole saw in the desired boring position (in the center of the opening at the end of the lateral pipe, or another position, for example) in the orthogonal direction inside the lateral pipe, and the boring position is sometimes displaced from the desired position.
Particularly when the pipe lining material blocking the opening of the lateral pipe has a hard surface, the hole saw can slip and move in the direction orthogonal to the longitudinal direction of the lateral pipe due to rotational recoil, and can collide with the internal peripheral surface of the lateral pipe. In this case, the hole saw is damaged, the pipe lining material suffers damage when a lateral pipe is being lined, or other such drawbacks occur.
An object of the present invention is therefore to provide a boring device whereby a boring blade can be easily and reliably positioned when a pipe lining material that blocks the opening at the end of a lateral pipe is bored through, and whereby the boring blade can be prevented from colliding with the internal peripheral surface of the pipe.